Final answer:
Muscle weakness and reduced bone strength in the elderly are primarily due to decreased vitamin D3 production, which leads to impaired bone formation and osteoporosis. Sarcopenia, the decline in muscle mass with age, also contributes to muscle weakness. Decreases in melanin, sebum production, and skin thickness are related to aging but do not directly affect muscle or bone strength.
Step-by-step explanation:
Muscle Weakness and Bone Strength Reduction in the Elderly
The muscle weakness and reduction in bone strength observed in the elderly can be attributed to a decrease in vitamin D3 production. Vitamin D3 is critical for calcium absorption, and without it, there can be an inadequate formation of new bone by osteoblasts. Factors such as poor diet, specifically low intake of calcium and vitamin D, can lead to impaired bone formation and conditions such as osteoporosis, characterized by decreased bone density and increased skeletal weakness and fractures.
Furthermore, sarcopenia is the gradual decrease in the ability to maintain skeletal muscle mass that occurs in later adulthood, likely resulting from a combination of satellite cell failure and a decrease in the availability of critical growth factors needed to maintain muscle mass. While multiple factors can contribute to muscle weakness and bone strength reduction, the decrease in vitamin D3 production is a primary factor that can lead to these conditions in the elderly.
The other options listed, such as melanin production, sebum production, and skin thickness, while indicative of aging, do not directly cause muscle weakness and reduced bone strength.